FORMATIOM, AND STEREOCHEMISTRY, OF 1,2-O-(1-METHYL-1,2-ETHANEDIYL)-D-GLUCOSE ACETALS FORMED IN THE ACID-CATALYZED HYDROLYSIS OF O-(2-HYDROXYPROPYL)CELLULOSE

Article abstract of DOI:10.1016/0008-6215(84)85129-0

In the hydrolysis of O-(2-hydroxypropyl)cellulose, residues of D-glucose substituted with a single O-(2-hydroxypropyl) substituent at O-2 (irrespective of the pattern of additional substitution at O-3 or O-6) form 1,2-O-(1-methyl-1,2-ethanediyl)-α-D-glucose acetals.Based on the characteristics of 2-O-(2-hydroxypropyl)-D-glucose and derivatives thereof in aqueous acid, these bicyclic products are shown to comprise a mixture of two furanose and two pyranose species that differ widely in relative stability, depending on the chirality of C-8 of the 1,4-dioxane ring of the compounds.The order of stability is 1,2-O-<1-methyl-(R)-1,2-ethanediyl>-α-D-glucopyranose> 1,2-O-<1-methyl-(S)-1,2-ethanediyl>-α-D-glucofuranose> 1,2-O-<1-methyl-(S)-1,2-ethanediyl>-α-D-glucopyranose> 1,2-O-<1-methyl-(R)-1,2-ethanediyl>-α-D-glucofuranose.N.m.r. evidence indicates that the two pyranose derivatives possess the "H-inside" conformation.Acetal formation is less prominent in acidic methanol, although the relative stabilities of the products are similar.Possible mechanisms for these various acid-catalyzed transformations are discussed.